decay
n. uncountablen. the natural process of something breaking down or rotting. It happens when things like wood, food, or old buildings slowly fall apart over time.
n. the organic process of decomposition or the gradual decline in quality, power, or health. In scientific contexts, it refers to the spontaneous transformation of a radioactive substance into a different state.
The old wooden fence shows signs of decay.
The dentist explained that sugar is the primary cause of tooth decay in young children.
The abandoned factory stood as a monument to urban decay, its rusted beams and shattered windows reflecting the economic decline of the surrounding neighborhood.
Often used in the abstract to describe social or moral decline; in physics, it is frequently paired with 'radioactive'.